BackgroundFlywheel resistance training has become more integrated within resistance training programs in a variety of sports due to the neuromuscular, strength, and task-specific enhancements reported with this training.ObjectiveThis paper aimed to present the consensus reached by internationally recognized experts during a meeting on current definitions and guidelines for the implementation of flywheel resistance training technology in sports.MethodsNineteen experts from different countries took part in the consensus process; 16 of them were present at the consensus meeting (18 May 2023) while three submitted their recommendations by e-mail. Prior to the meeting, evidence summaries were developed relating to areas of priority. This paper discusses the available evidence and consensus process from which recommendations were made regarding the appropriate use of flywheel resistance training technology in sports. The process to gain consensus had five steps: (1) performing a systematic review of systematic reviews, (2) updating the most recent umbrella review published on this topic, (3) first round discussion among a sample of the research group included in this consensus statement, (4) selection of research group members-process of the consensus meeting and formulation of the recommendations, and (5) the consensus process. The systematic analysis of the literature was performed to select the most up-to-date review papers available on the topic, which resulted in nine articles; their methodological quality was assessed according to AMSTAR 2 (Assessing the Methodological Quality of Systematic Review 2) and GRADE (Grading Recommendations Assessment Development and Evaluation). Statements and recommendations scoring 7-9 were considered appropriate.ResultsThe recommendations were based on the evidence summary and researchers' expertise; the consensus statement included three statements and seven recommendations for the use of flywheel resistance training technology. These statements and recommendations were anonymously voted on and qualitatively analyzed. The three statements reported a score ranging from 8.1 to 8.8, and therefore, all statements included in this consensus were considered appropriate. The recommendations (1-7) had a score ranging from 7.7 to 8.6, and therefore, all recommendations were considered appropriate.ConclusionsBecause of the consensus achieved among the experts in this project, it is suggested that practitioners and researchers should adopt the guidelines reported in this consensus statement regarding the use of flywheel resistance technology in sports.

We tested the hypothesis that prolonged intermittent hand exposures to transient contrast thermal stimuli would enhance the finger cold-induced vasodilatation (CIVD) response during localized cooling. Eight healthy men participated in a 5-week regimen, during which they immersed, thrice per week, the non-dominant (EXP) hand in 8° and 43 °C water, sequentially and at 3-min intervals, for a total period of 60 min. The contralateral (i.e., dominant) hand served as the control (CON) hand. Before and after the regimen, subjects conducted two 30-min hand cold (8 °C water) provocation trials, one with the EXP hand and the other with the CON hand. In addition, a flow-mediated dilatation test was performed in the brachial artery of the EXP arm. Regardless of the hand tested, the average finger skin temperature [CON hand: pre-trial = 10.5 (1.2)°C, post-trial = 10.8 (1.3)°C and EXP hand: pre-trial = 10.7 (1.1)°C, post-trial 10.9 (1.1)°C; p = 0.79], and the incidence of CIVD events [CON hand: pre-trial = 1.1 (1.2) events, post-trial = 1.2 (1.1) events and EXP hand: pre-trial = 1.1 (0.8) events, post-trial = 1.1 (0.8) events; p = 0.88] were not affected by the 5-week regimen. The sensation of cold-induced pain was transiently alleviated following the regimen (p = 0.02). The flow-mediated dilatation response of the EXP brachial artery remained unaltered [pre-trial = 5.4 (3.2)%, post-trial = 4.7 (3.6)%; p = 0.51]. Therefore, five weeks of intermittent hand exposures to alternating cold and hot stimuli do not improve finger temperature responsiveness to sustained localized cold.

Introduction Foot-borne soldiers sometimes carry out nighttime operations. It has previously been reported an elevated metabolic demand and impaired walking economy during outdoor walking on a gravel road in darkness wearing night vision goggles (NVG), compared with wearing a headlamp. The aim of the present study was to evaluate the effect of wearing NVG while walking in a hilly forest terrain and compare the results between experienced and inexperienced NVG users.Materials and Methods At nighttime, two different groups, inexperienced (five men and six women) and experienced (nine men) NVG users, walked 1.1 km at a self-selected comfortable pace in a hilly forest. Part I was mainly uphill, and Part II was mainly downhill. Walks were performed wearing a headlamp (light), monocular NVG (mono), binocular NVG (bino), or mono with a 25 kg extra weight (backpack). Walking economy calculated from oxygen uptake in relation to body mass and covered distance (VO2 (mL/[kg  km])), heart rate, gait, and walking speed were measured.Results In both groups, walking economy was deteriorated in all three conditions with limited vision (mono, bino, and backpack) compared to the light condition, both during Part I (mono/bino, experienced: +26/+25%, inexperienced: +34/+28%) and Part II (mono/bino, experienced: +44/+46%, inexperienced: +63/+49%). In the backpack condition, the relative change of walking economy was greater for the inexperienced group than the experienced group: Part I (experienced: +46%, inexperienced: +70%), Part II (experienced: +71%, inexperienced: +111%). Concurrently, the step length was shorter in all three conditions with limited vision during Part I (mono/bino/backpack, experienced: -7/-7/-15%, inexperienced: -12/-12/-19%) and Part II (mono/bino/backpack; experienced: -8/-8/-14%, inexperienced: -17/-15/-24%) than in the light condition. The experienced NVG users walked faster during all conditions, but there was no difference in heart rate between groups.Conclusions Despite that foveal vision using NVG is adequate, it appears that the mechanical efficiency during nighttime walking in hilly terrain was markedly lower while wearing NVG than with full vision, regardless of whether the soldier was an experienced or inexperienced NVG user. Moreover, the walking economy was even more affected when adding the 25-kg extra weight. It is probable that the deteriorated mechanical efficiency was partly due to the shorter step length in all three conditions with limited vision.

INTRODUCTION: For tactical reasons, the foot-borne soldiers sometimes undertake nighttime operations. However, the metabolic demand during walking in complete darkness may be markedly increased. The purpose of this study was to investigate if metabolic demand and kinematics would change while walking on a gravel road and a slightly hilly trail in darkness with or without visual aid.

MATERIALS AND METHODS: Fourteen cadets (11 men and 3 women, age: 25 ± 7 years, height: 178 ± 8 cm, and weight: 78 ± 13 kg) walked at 4 km/h on a straight gravel road and on a slightly hilly forest trail (n = 9). Both trials were performed at nighttime under four different conditions, wearing a headlamp (Light), blindfold (Dark), monocular (Mono), or binocular (Bino) night vision goggles. During the 10-minute walks, oxygen uptake, heart rate, and kinematic data were assessed. Ratings of perceived exertion, discomfort, and mental stress were evaluated after each condition using a category ratio scale. Physiologic and kinematic variables were evaluated using repeated-measures analysis of variance, whereas ratings were evaluated using non-parametric Friedman analysis of variance.

RESULTS: Oxygen uptake was higher in all three conditions with no or limited vision (Dark, Mono, and Bino) than in the Light condition (P ≤ 0.02) when walking on both the gravel road (+5-8%) and the forest trail (+6-14%). Heart rate was higher during the Dark than during the Light condition when walking on the forest trail, whereas there was no difference between conditions on the gravel road. During both trials, gait frequency was higher during the Dark than during the Light, Mono, and Bino conditions. Ratings were generally low during all conditions.

CONCLUSIONS: Walking on a gravel road or a forest trail wearing a blindfold or visual aid increased the metabolic demand. Thus, it appears that the metabolic demand is higher during overground walking with night vision goggles than with full vision, which may influence the performance of nighttime operations.

Resistance exercise on Earth commonly involves both body weight and external load. When developing exercise routines and devices for use in space, the absence of body weight is not always adequately considered. This study compared musculoskeletal load distribution during two flywheel resistance knee-extension exercises, performed in the direction of (vertical squat; S) or perpendicular to (horizontal leg press; LP) the gravity vector. Eleven participants performed these two exercises at a given submaximal load. Motion analysis and musculoskeletal modelling were used to compute joint loads and to simulate a weightless situation. The flywheel load was more than twice as high in LP as in S (p < 0.001). Joint moments and forces were greater during LP than during S in the ankle, hip and lower back (p < 0.01) but were similar in the knee. In the simulated weightless situation, hip and lower-back loadings in S were higher than corresponding values at Earth gravity (p ≤ 0.01), whereas LP joint loads did not increase. The results suggest that LP is a better terrestrial analogue than S for knee-extension exercise in weightlessness and that the magnitude and direction of gravity during resistance exercise should be considered when designing and evaluating countermeasure exercise routines and devices for space.

It is anticipated that flywheel-based leg resistance exercise will be implemented in future long-duration space missions, to counter deconditioning of weight-bearing bones and postural muscles. The aim was to examine low back loads and muscle engagements during flywheel leg press (FWLP) and flywheel squat (FWS) and, for comparisons, free-weight barbell back squat (BBS). Eight resistance-trained subjects performed 8 repetition maximums of FWLP, FWS, and BBS. Motion analysis and inverse dynamics-based musculoskeletal modeling were used to compute joint loads and muscle forces. Muscle activities were measured with electromyography (EMG). At the L4–L5 level, peak vertebral compression force was similarly high in all exercise modes, whereas peak vertebral posteroanterior shear force was greater (p < 0.05) in FWLP and BBS than in FWS. Among the back-extensor muscles, the erector spinae longissimus exerted the greatest peak force, with no difference between exercises. Peak force in the lumbar multifidus was lower (p < 0.05) during FWLP than during FWS and BBS. Peak EMG activity in the lumbar extensor muscles ranged between 31 and 122% of maximal voluntary isometric contraction across muscles and exercise modes, with the greatest levels in the lumbar multifidus. The vertebral compression forces and muscle activations during the flywheel exercises were sufficiently high to presume that when implementing such exercise in space countermeasure regimens, they may be capable of preventing muscle atrophy and vertebral demineralization in the lumbar region.

INTRODUCTION: Uniformed services commonly perform foot-borne operations at night, while using visual aid in terms of night vision goggles (NVG). During slow-level walking, complete lack of visual input alters kinematics and markedly increases the metabolic demand, whereas the effect on kinematics and energy expenditure of restricting the peripheral visual field by wearing NVG is still unknown. The purpose was to evaluate whether metabolic demands and kinematics during level walking are affected by complete darkness with and without visual aid.

MATERIALS AND METHODS: Eleven healthy men walked on a treadmill (inclination: +2.3°, velocity: 4 km/h) with full vision in a lighted laboratory (Light), and in complete darkness wearing either a blindfold (Dark), or restricting the visual field to about 40° by wearing monocular (Mono) or binocular (Bino) NVG. Oxygen uptake ($\dot{\text{V}}$O2) was measured to evaluate metabolic demands. Inertial measurement units were used to estimate kinematics, and the outcome was validated by using a motion capture system. Ratings of perceived exertion, discomfort, and mental stress were evaluated after each condition using a Borg ratio scale. Physiologic and kinematic variables were evaluated using repeated measures analysis of variance (ANOVA), whereas ratings were evaluated using non-parametric Friedman ANOVA.

RESULTS: $\dot{\text{V}}$ O2 was 20% higher in the Dark (1.2 ± 0.2 L/min) than the Light (1.0 ± 0.2 L/min) condition. Nominally, $\dot{\text{V}}$O2 in the Mono (1.1 ± 0.2 L/min) and Bino (1.1 ± 0.2 L/min) conditions fell in between those in the Light and Dark conditions but was not statistically different from either the Light or the Dark condition. Step length was shorter in the Dark (-9%, 1.22 ± 0.16 m) and Mono (-6%, 1.27 ± 0.09 m) conditions than in the Light condition (1.35 ± 0.11 m), whereas the Bino (1.28 ± 0.08 m) condition was not statistically different from either the Light or the Dark condition. The three conditions with no or limited vision were perceived more physically demanding, more uncomfortable, and more mentally stressful than the Light condition, and the Dark condition was perceived more mentally stressful than both NVG conditions.

CONCLUSIONS: The study confirms that complete lack of visual cues markedly reduces the mechanical efficiency during level walking, even under obstacle-free and highly predictable conditions. That $\dot{\text{V}}$O2 and step length values for the NVG conditions fell in between those of the Light and Dark conditions suggest that both foveal and peripheral vision may play important roles in optimizing the mechanical efficiency during level walking.